Code
var query = from s in context.Subject.Include("Reply")
                            where s.Id == subjectId
                            //orderby s.Reply.OrderBy(r => r.PostTime)
                            select s;
/*
我想以reply中的posttime排序，但不知道怎么弄。
注：reply的数据类型为System.Data.Objects.DataClasses.EntityCollection<SubjectReply> 

*/

//现在我是这样实现的：
var query = from s in context.ZoneSubject.Include("Reply")
                            where s.Id == subjectId
                            select s;
                Subject subject = query.FirstOrDefault();
                if (subject != null)
                {
                    var q = from r in context.SubjectReply
                            where r.Subject.Id == subjectId
                            orderby r.PostTime ascending
                            select r;
                    foreach (var item in q)
                    {
                        subject.Reply.Add(item);
                    }
                }
                return subject;
//如何将它改简短点，高人请指点？